A review of resin features in radiata pine

In pine trees, resin is formed in an interconnecting system of tube-like structures known as resin canals. In radiata pine (Pinus radiata D.Don) these are most common in the earlywood/latewood transition zone and within the latewood. Within and between-tree variation in resin canal occurrence has been poorly documented and little is known about factors controlling canal frequency or the relationship between canal distribution and the formation of timber blemishes. The presence of resin canals is often associated with the formation of resinous defects of various kinds which can cause major losses in timber production of particularly appearance-grade wood products. This review summarises recent studies of radiata pine, which have shown that:

• the formation of resin canals and resinous blemishes on stems and in wood is more frequent in hotter, drier sites subject to water stress. It is also influenced by silvicultural procedures (stocking rate and thinning) and genetic constitution;

• external signs of resin bleeding on stems may indicate the presence of internal resin blemishes that degrade timber products. Some companies now record external resin bleeding in forest inventory systems in order to improve harvest planning. Such data are used to guide pruning intensity and the selection of genotypes in breeding programmes;

• resinous blemishes on log ends can be an indication of internal defects in radiata pine timber. These include resin pockets, resin patches, galls, blemishes and intra-ring checks. Some companies now segregate logs in the log yard by visual inspection of log ends; and

• certain types of resin features are sometimes associated with external lesions and dimpling on the log surface.